1. Field of the Invention
The invention relates generally to mining and specifically to the removal of bitumen from rocks, sands and clay.
2. Description of the Prior Art
Vast deposits of oil exist throughout the world, and especially in Canada, as thick, heavy oil, in the form of bitumen mixed with solid minerals and water. The tar sands that hold the bitumen contain rich amounts of valuable minerals, especially alumina, in the sand itself. The sands include a fines fraction, defined as particles less than forty-four microns, that have a clay component (0-2 microns) and a silica fine sand component (2-44 microns). High bitumen content in the tar sand is usually associated with a low fines fraction. Conversely, a low bitumen content in the tar sand is usually associated with a high fines content.
Typically in the fines fraction there are found two parts silica fine sand component to one part clay component, e.g., one-third is clay. About thirty-five percent of such clay is alumina. Certain low grade ores, conventionally comprised of undifferentiated silica fine sand and clay, have as little as six percent alumina in the fines fraction. Such fines fractions are a problem when used in exothermic reactions that separate out the alumina. Fines fractions, with more than ten percent alumina, are much more easily processed with exothermic reactions. Therefore, it is desirable to have a bitumen separation process that can produce tar sands clays separated from fine sand.
John S. Rendall, the present inventor, describes in U.S. Pat. No. 4,424,112, issued Jan. 3, 1984, a method and apparatus for solvent extraction of bitumen oils from tar sands and their separation into synthetic crude oil and synthetic fuel oil. Tar sands are mixed with hot water and a solvent to form a slurry while excluding substantially all air. The slurry thus contains sand, clay, bitumen oils, solvent and water. This slurry is separated into bitumen extract, which includes bitumen oils, solvent and water, and a solids extract containing sand, clay, solvent and water. The bitumen extract is processed to selectively remove the water and fines. The bitumen extract is then processed to remove the solvent for recycle, and the bitumen as crude oil. Water is separated from the bitumen and solid extracts and is also reused.
A hot water bitumen extraction process is described by John S. Rendall in U.S. Pat. No. 4,875,998, issued Oct. 24, 1989. Crushed tar sands are conditioned in hot water while excluding air. Oversized and inert rocks are removed by screening. A water immiscible hydrocarbon solvent is used to extract the bitumen content to form a bitumen extract phase, a middle water phase, and a lower spent solids phase, each of which are processed for bitumen oils and to recover solvent and water for reuse.
A method of extracting valuable minerals and precious metals from oil sands ore bodies is described by John S. Rendall and Valentine W. Vaughn, Jr., in U.S. Pat. No. 5,124,008, issued Jun. 23, 1992. Both coarse and fine sand fractions are produced after extracting the hydrocarbons, and both fractions contain valuable minerals and precious metals. These fractions are agglomerated with concentrated sulfuric acid and leached. The sulfuric acid mother leach liquor is processed to remove sulfate crystals of aluminum, iron and titanyl, while recycling the raffinate. The aluminum sulfate crystals are converted to cell-grade alumina product.
In United States patent application, Ser. No. 08/356,148, filed Dec. 15, 1994, John S. Rendall and Steven J. Lane describe a system and method for immediately separating oil sands into three layers using a logwasher with paddles that mix the oil sands with hot water and steam. The three layers of: bitumen, clay/sand/water slurry, and rock, effectively and immediately separate and are not re-mixed in further processing as was conventional. A clay fraction from the fines is further produced for mineral processing.
Canadian Patent Application, 2,165,252, of Steven J. Lane, which was laid open Jul. 16, 1997, describes a method of oil sands separation. Such method comprises introducing pre-sized oil sands into one end of a vessel. The oil sands are moved towards a solids outlet in the vessel while breaking up lumps in the oil sands. The solids are compressed at the solids outlet by maintaining a head of solids above a restriction in a hopper. Steam is introduced into the vessel to maintain the temperature of the interior of the vessel such that separation of bitumen from solids takes place, while gas dissolved in the bitumen nucleates and forms entrained gas bubbles within the bitumen that cause flotation of the bitumen. Hot water is introduced into the vessel and removes middlings from the central zone of the vessel to maintain viscosity of the central zone of the vessel such that bitumen and entrained gases rise through the central zone of the vessel to form a surface layer on the material in the vessel. The floating bitumen with entrained gases is then skimmed from the surface layer.